//  Copyright 2024 International Digital Economy Academy
// 
//  Licensed under the Apache License, Version 2.0 (the "License");
//  you may not use this file except in compliance with the License.
//  You may obtain a copy of the License at
// 
//      http://www.apache.org/licenses/LICENSE-2.0
// 
//  Unless required by applicable law or agreed to in writing, software
//  distributed under the License is distributed on an "AS IS" BASIS,
//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
//  See the License for the specific language governing permissions and
//  limitations under the License.

///|
pub fn fib(n : Int) -> Int64 {
  loop (0L, 1L, n) {
    (a, _, 0) => a
    (a, b, n) => continue (b, a + b, n - 1)
  }
}
